Due in part to recent environmental concerns, water-based products are seeing increasing use in the printing industry, the papermaking industry and the coatings industry. However, aqueous systems are slow-drying and result in lower production speeds than solvent systems. It has thus been necessary to constantly adapt aqueous systems to the higher speeds entailed by productivity improvements, creating a desire for performance enhancements in inks and paper coatings suitable for high-speed printing and high-speed coating. Such circumstances have led to a need, in connection with water-based inks and water-based coatings, for surfactants which, in order to impart substrate wettability, penetrability and dispersibility, possess an excellent surface tension-lowering ability. In selecting a surfactant, it is very important that the resulting system have a static surface tension when at rest, and also, given the above productivity enhancement-driven need for higher printing speeds, that the system have a low dynamic surface tension during high-speed use.
Acetylene glycol-type surfactants, such as acetylene glycol and its ethylene oxide derivatives, are currently used as wetting agents and dispersing agents in inks and coatings because they achieve a balance in their ability to lower both the static surface tension and the dynamic surface tension, are substantially free of the drawbacks of existing nonionic and anionic surfactants, and are also foam-inhibiting.
Because of such problems as their low solubility in water or their solid state at normal temperatures, acetylene glycol-type surfactants are used together with a solubilizing agent, such as polyethylene glycol, polyoxyethylene nonyl phenyl ether, or polyoxy(ethylene-propylene) block polymer—which is compatible as well with environmental concerns. This surfactant-solubilizer combination, when added to a water-base ink or paper coating, imparts the system with self-emulsifiability.
However, because the triple bonds in the surfactant structure have a strong affinity to metals, when such formulations of an acetylene glycol-type surfactant with a solubilizer are used in inkjet inks, the ink nozzles clog due to surfactant residues. Similarly, when such formulations are incorporated into paper coatings, residues remain on the coating rolls, causing uneven coating.
Prior-art references relating to the present invention include JP-A 2002-348500.